1. Field of the Invention
The present invention relates to a light emitting module realizing improved light coupling efficiency and a single-fiber two-way optical communication module having the light emitting module and used for two-way optical communication of a plurality of waves performed by a single fiber.
2. Description of the Related Art
Hitherto, in an optical fiber communication system, a two-way optical communication module is used for an access network system of telephone communication or the like (refer to, for example, Japanese Patent Application National Publication Laid-open No. 2003-524789).
In an optical communication module disclosed in Japanese Patent Application National Publication Laid-open No. 2003-524789, a light emitting module and a light receiving module which are held in a single casing transmit/receive light via a lens coupling optical device and a beam splitter disposed close to an end of an optical fiber. Each of the light emitting module, the light receiving module, and the optical fiber does not have a mechanism of adjusting the optical axis direction, and the light emitting module and the light receiving module are parts separate from the casing.
In the optical communication module, the optical axis direction of the light emitting module is not adjusted, so that the coupling efficiency varies. Since an optical filter is inserted in nonparallel rays, aberration occurs and the coupling efficiency is low. Accordingly, the light coupling efficiency of the optical communication module is low. Since the optical axis direction of the light receiving module is not adjusted, light receiving efficiency of the light receiving module is low. Consequently, in the optical communication module, the light coupling efficiency varies.